U.S. patent application number 14/271870 was filed with the patent office on 2014-08-28 for applying biaxially oriented polyester onto a metal substrate.
The applicant listed for this patent is Mark V. Loen, Jan K. Moritz, James E. Velliky. Invention is credited to Mark V. Loen, Jan K. Moritz, James E. Velliky.
Application Number | 20140238601 14/271870 |
Document ID | / |
Family ID | 51386934 |
Filed Date | 2014-08-28 |
United States Patent
Application |
20140238601 |
Kind Code |
A1 |
Loen; Mark V. ; et
al. |
August 28, 2014 |
Applying Biaxially Oriented Polyester onto a Metal Substrate
Abstract
The invention is a laminating process which is directed toward
economical production methods for scalable amounts of production
which develop properties suitable for a broad based product line.
In particular, the product is capable of important key components
of commercial properties such as adhesion, scratch resistance,
chemical inertness, and bending without failure.
Inventors: |
Loen; Mark V.; (Maricopa,
AZ) ; Velliky; James E.; (Jacksonville, FL) ;
Moritz; Jan K.; (North Kingstown, RI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Loen; Mark V.
Velliky; James E.
Moritz; Jan K. |
Maricopa
Jacksonville
North Kingstown |
AZ
FL
RI |
US
US
US |
|
|
Family ID: |
51386934 |
Appl. No.: |
14/271870 |
Filed: |
May 7, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13759538 |
Feb 5, 2013 |
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14271870 |
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13108584 |
May 16, 2011 |
8404064 |
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13759538 |
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12388011 |
Feb 18, 2009 |
7942991 |
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13108584 |
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11530723 |
Sep 11, 2006 |
7678213 |
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12388011 |
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60716053 |
Sep 13, 2005 |
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Current U.S.
Class: |
156/322 |
Current CPC
Class: |
B32B 27/08 20130101;
B32B 15/18 20130101; B32B 2367/00 20130101; B32B 38/162 20130101;
B32B 38/105 20130101; B32B 27/36 20130101; B32B 2307/518 20130101;
B32B 2310/0825 20130101; B32B 2307/406 20130101; B32B 37/206
20130101; B32B 2307/714 20130101; B32B 2307/584 20130101; B32B
15/09 20130101; B32B 37/06 20130101; B32B 2309/02 20130101; B32B
39/00 20130101; B32B 37/04 20130101; B32B 37/003 20130101; B32B
37/08 20130101; B32B 38/185 20130101; B32B 2309/10 20130101; B32B
2310/0445 20130101; B32B 2305/30 20130101; B32B 2307/546 20130101;
B32B 2309/14 20130101; B32B 2309/72 20130101; B32B 2311/00
20130101; B32B 2310/0812 20130101; B32B 2309/105 20130101 |
Class at
Publication: |
156/322 |
International
Class: |
B32B 37/14 20060101
B32B037/14 |
Claims
1. A method of laminating a biaxially oriented polyester film onto
a metal substrate to create desirable simultaneous commercial
properties comprising: a. creating a biaxially oriented polyester
film on a film manufacturing line, b. wherein said biaxially
oriented polyester film has desirable commercial properties, c.
increasing the surface energy of at least one major side of said
metal substrate to a bonding level on a metal lamination line, d.
preheating said metal substrate to at least 200.degree. F., e.
pressing said biaxially oriented polyester film onto said at least
one major side by use of a roll, f. thereby creating a metal
polymer laminate, g. wherein said biaxially oriented polyester film
is primarily thermoplastic polyester by weight, h. wherein said
biaxially oriented polyester film comprises at least one layer, i.
wherein said biaxially oriented polyester film comprises at least
one of PET, PBT, PETG, and PETI, j. post treating said metal
polymer laminate by heating said metal polymer laminate to at least
a bonding temperature of said biaxially oriented polyester film to
said metal substrate, wherein said bonding temperature is below a
melting temperature of a layer of said biaxially oriented polyester
film that is contacting said metal substrate, k. wherein said post
treating of said metal polymer laminate preserves crystallinity in
said biaxially oriented film according to a predetermined
criterion, and l. cooling said metal polymer laminate, whereby said
metal polymer laminate has said desirable simultaneous commercial
properties after said cooling comprising: m. bonding of said
biaxially oriented polyester film onto said metal substrate of at
least 43 ounces per inch, n. a pencil hardness of at least 2B, and
o. successfully passing metal can pack testing for at least thirty
days.
2. The processing steps according to claim 1 wherein any said bond
between said biaxially oriented polyester film and said metal
substrate is created by use of an amorphous polyester.
3. The processing steps according to claim 2 wherein said bond
between said biaxially oriented polyester film and said metal
substrate is created by use of a PETI or PETG in a film layer in
contact with said metal substrate.
4. The processing steps according to claim 1 wherein any said
biaxially oriented polyester film is trimmed to substantially match
the width of said metal substrate prior to being pressed against
said metal substrate.
5. The processing steps according to claim 1 wherein said metal
lamination line is either a continuous operation or a batch
operation.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation in part of U.S.
application Ser. No. 13/759,538 filed on Feb. 5, 2013, which is a
divisional of U.S. Pat. No. 8,404,064, Filed on May 16, 2011, which
is a continuation in part of U.S. Pat. No. 7,942,991 filed on Feb.
18, 2009, which is a continuation in part of U.S. Pat. No.
7,678,213 filed on Sep. 11, 2006, which claims the benefit of U.S.
Provisional Application No. 60/716,053 filed on Sep. 13, 2005. All
referenced applications are incorporated herein by reference.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
REFERENCE TO SEQUENCE LISTING, A TABLE, OR COMPUTER PROGRAM
LISTING
[0003] Not applicable.
BACKGROUND OF THE INVENTION
[0004] (1) Field of the Invention
[0005] This application is directed to laminating films in the
solid state onto metal substrates. In particular, applying
bi-axially oriented polyester films onto metal substrates to create
a chemical bond on an industrial processing line whereby multiple
desirable commercial properties are simultaneously developed.
[0006] (2) Description of Related Art
[0007] Others have described laboratory processing steps related to
putting films onto metal surfaces. For example, U.S. Pat. No.
5,330,605 describes preheating a metal strip and then laminating a
biaxially oriented copolyester resin film. However, a post treating
step has been found to be necessary for permanent commercial
adhesion in many important markets, and the post treating step is
troublesome when used with an oriented polyester film due to
crystalline property changes. It is difficult to obtain sufficient
bonding for demanding stamping applications with the additional
demanding chemical resistance requirements. Since crystallinity
provides important commercial pencil hardness, toughness, and
chemical resistance properties, a high temperature post heating
step will change the crystallinity in actual use.
[0008] U.S. Pat. No. 5,149,389 and U.S. Pat. No. 5,093,208
describes a thermal laminating process where a metal strip is
preheated, laminated, post heated, and quenched in water. The
process targets the creation of non-crystalline polyester coating
that is generally useful for can making. Unfortunately, the lack of
crystallinity is a distinct disadvantage in creating desirable
simultaneous commercial characteristics such as pencil hardness,
adhesion, and chemical resistance.
[0009] U.S. Pat. No. 5,318,648 describes a thermal laminating
process where the cooling process is specifically performed to
avoid creating crystallinity in the laminate film. This has similar
problems with pencil hardness and chemical resistance properties
just described.
[0010] U.S. Pat. No. 3,679,513 describes a thermal laminating
process for a polyethylene. The process does not describe
pretreating the metal surface by raising the surface energy nor
does it describe methods of creating crystallinity in the finished
laminate film to develop pencil hardness or bending toughness.
Polyethylene is not known to develop desirable commercial
properties and the low melting point of polyethylene is undesirable
for many markets when compared to other polymers.
[0011] U.S. Pat. No. 5,679,200 describes a thermal laminating
process for applying a film to a metal strip where the laminating
rolls provide a specific force. The patent is directed toward a
specific laminating nip force related to avoiding the pickup of
film onto the nip rolls. The process does not describe pretreating
the metal surface by raising the surface energy nor does it
describe methods of creating crystallinity in the finished laminate
film.
[0012] U.S. Pat. No. 5,695,579 describes a thermal laminating
process where the polymer coated metal is rapidly and immediately
quenched after post treating to ensure that the coating is
amorphous. The described process is designed to avoid creating
crystallinity in the finished laminate film. The process does not
describe pretreating the metal surface by raising the surface
energy nor does it describe methods of creating crystallinity in
the finished laminate film.
[0013] Others have worked on important commercial--technical issues
such as the eliminating entrapped air between the film and metal
substrate. For example, U.S. Pat. No. 6,200,409 describes an
improved laminating process which works on eliminating air bubbles
by heating the laminating nip rolls and preheating the film prior
to laminating. Similarly, U.S. Pat. No. 6,164,358 describes efforts
at reducing air entrapment by using a support roll with a projected
film angle. In this disclosure, a commercially acceptable amount is
defined as an 8% area covered by entrapped air. Others, such as
U.S. Pat. No. 5,679,200, have attempted to handle trapped air
through increased nip forces.
[0014] Important commercial markets are open to a laminate provided
that acceptable adhesion, pencil hardness, and corrosion protection
can be simultaneously achieved. These markets are currently served
by the pre-painted coil coated industry. Typical products include
the following: Building and Construction Products, Transportation
Products, Business and Consumer Products.
[0015] In particular, Containers and Packaging Products such
as:
a. Cans, Ends, Tabs, Crowns, & Closures b. Barrels, Drums &
Pails c. Strapping & Seals, and d. Draw & Ironed can bodies
are important markets that can be served by a laminate from a
laminating process.
[0016] It is important to note that the referenced patents have not
resulted in a commercially viable high production thermal
laminating line in the US. The difficulties in simultaneously
scaling up production, creating an economically viable process, and
developing suitable commercial properties have been strong barriers
to the actual implementation of a laminating process. The previous
efforts by others have been lacking in important technical aspects
of cooperation between the processing steps, economic viability,
and suitable commercial properties. In particular, film properties
have not been carefully designed to work with processing steps that
foster high levels of adhesion and chemical inertness.
[0017] Current high production laminating methods in the United
States address metal substrates, i.e. 0.005'' and above, are
primarily directed at utilizing press on adhesives which are
applied by a roller onto the metal substrate, and the adhesive is
dried in an oven prior to the laminating step. This process is
commonly added to, or is a part of, a commercial coil paint line.
The application of the film to the metal substrate is generally
done close to ambient temperatures. The adhesive is separately
applied to the metal substrate and is usually not a part of the
film, such as a multilayer film.
[0018] It is important that high production thermal laminating
methods have little or no visible entrapped air between the metal
substrate and the film. Entrapped air causes thinning of the
coating at an unpredictable amount. In particular, when a formed
part is bent and the bend occurs where an air bubble exists in the
coating, an increased likelihood of failure results. Air entrapment
is a serious issue when the air bubble size is significant relative
to the coating thickness, and the frequency is high. It is also
visually disturbing at an 8 percent level to a customer, on a
surface area basis, and raises unnecessary questions about process
control.
[0019] It is important that the coating has the necessary pencil
hardness, that is, surface scratch resistance, formability, and
suitable chemical resistance. Coating hardness must be balanced
against brittleness. A hard coating has an increased likelihood of
splitting on the bend of a formed part. If the coating splits, the
metal is exposed and there is likelihood of a corrosive failure at
that spot.
[0020] In summary, it has been difficult to develop the necessary
simultaneous properties for a commercial thermoplastic coating on a
thick metal substrate at an economical cost. The coating needs the
simultaneous capability of: developing suitable bonding to the
metal substrate, economical production, having suitable pencil
hardness, eliminating air entrapment, obtaining a high level of
chemical resistance, and having the ability to withstand a tight
metal bend without splitting.
BRIEF SUMMARY OF THE INVENTION
[0021] The invention is a laminating process which is directed
toward economical production methods at scalable amounts of
production which develop properties suitable for a product line
with demanding chemical resistance properties. In particular, the
product is capable of important key components of commercial
properties such as adhesion, scratch resistance, chemical
inertness, eliminating air entrapment, and bending without
failure.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)
[0022] FIG. 1 shows an embodied commercial line.
[0023] FIG. 2 shows a general embodiment of the invention.
[0024] FIGS. 3A-3B show various embodied layer configurations.
[0025] FIG. 4 shows an embodied laminating station.
DETAILED DESCRIPTION OF THE INVENTION
[0026] The invention is a laminating process that simultaneously
creates desirable commercial products in a crystalline polyester
film due to its unique composition as an affordable engineered
polymer. In particular, essential commercial characteristics of
scratch resistance, chemical inertness, and permanent adhesion can
be developed which are highly competitive to paint. Polyester is
generally more affordable than other engineered polymers in the
marketplace, and is chemically similar to many paints which are
short chain polyesters admixed with cured epoxies.
[0027] When considering current pricing trends in thermoplastics,
the better priced plastics tend to be polyethylene (high density,
low density, linear low density), polystyrene, polypropylene, ABS,
acetal homopolymer, and polyester (both PET and PBT). This is in
reference to the types of polymer grades that are reasonably
available in volume pricing that are extrudable at a commercial
speed for a thermoplastic coating of about 0.5 to 8.0 mils thick.
However, it has been found difficult to find satisfactory coating
performance among many of the lower priced polymers, in particular,
the polyolefins. Surface scratch resistance, in particular, has
been elusive.
[0028] The higher priced polymers, such as Acrylic, Fluoropolymers,
Liquid Crystal Polymers, Polyamide/imide, Polyarylate,
Polyetherimide, Polyetherketone, Polyphenylene Sulfide,
Polysulfone, Cellulosics, Polycarbonate and Polyurethane are
financially unappealing. However, these polymers can be applied
with satisfactory results by using tie layers and the teachings of
this invention.
[0029] Table 1 shows a rough affordability ratio for the same
coating thickness on a price per pound when additionally
considering the polymer specific gravity. Although Table 1 could be
shown as various ranges depending upon the polymer grades chosen,
it is a rough average for a simplified view.
TABLE-US-00001 TABLE 1 Polyethylene 1 Polypropylene 1 ABS 1.1 PVC
1.3 Polystyrene 1.3 APET 1.4 Acrylic 1.4 Polyester 1.6 Acetal 1.9
Nylon 6/6 2.0 Polyurethane 2.2 Polycarbonate 2.4
[0030] Biaxially-oriented polyethylene terephthalate (also referred
to as BoPET) is a polyester film made by stretching a film made
from polyethylene terephthalate (PET) to create better properties
such as tensile strength and superior chemical resistance by adding
desirable crystallinity. BoPET is made on a manufacturing process
line that begins with an extruded polyester film and is immediately
quenched by a chill roll. In this initial condition, the polyester
film is relatively amorphous with little crystallinity. To create a
BoPET film, the solid film is stretched in the machine direction
(i.e. down its length) and subsequently in the transverse direction
(across the width) in a two-step process. In both steps the film is
heated to a particular temperature, typically above 390.degree. F.,
and dimensionally stretched in both directions.
[0031] Once the film has been stretched, it is then processed
through an oven to create and set desirable crystalline properties.
By creating the proper crystalline properties, the end result is an
oriented film with desirable commercial mechanical and chemical
resistance properties that are useful in a variety of markets,
particularly the food and beverage can market.
[0032] In an important embodiment of the invention, it was
discovered that it was possible to laminate the BoPET film to a
metal substrate at a post heat temperature lower than the BoPET
film melting temperature. A tie layer could be included in the
film, but also a mono layer BoPET film could equally be bonded
under the right processing conditions.
[0033] FIG. 1 an example of a continuous metal lamination line. It
is generally conceived that the process will be continuous (such as
shown in FIG. 1) or a batch process (without the looping towers
shown in FIG. 1). Looping (storage) towers can be used at each end
of the line, or at one end of the line such as the entry end.
[0034] The major processing sections are cleaning, raising the
surface energy (if needed after cleaning), preheating, laminating,
post heating, and cooling. The type of film used in this invention
is generally conceived as BoPET. The process section would include
needed control for processing parameters, such as temperature, and
line control that would marry the film and processing parameters
for the commercial end result to achieve high bonding and chemical
resistance.
[0035] The material handling sections comprise tension control
units, steering units, film unwinding/rewinding, splicing
equipment, idler rolls, and shearing equipment.
[0036] Line support equipment and processes are also utilized,
which includes water cooling systems, air compressors, hydraulic
systems, venting equipment, heating and cooling equipment, control
systems, operator stations, electrical systems, water supply
systems, electrical and gas supply systems, testing equipment, coil
handling equipment, cranes, order entry equipment, tagging and
inventory control, etc.
[0037] The production line sequence follows. The film is unwound
from one of two payoff reels 101 and then fed through threading
pinch rolls 102 to an entry strip shear. Here the strip is sheared
103 in readiness for splicing 104 by a welder, joiner, or other
strip connecting means. The strip then goes through an entry
looping tower 107. A pair of bridle rolls 105a,b provide tension
control on either side of the entry looping tower 118, and a
steering roll 106a provides strip tracking control. The strip
proceeds through a cleaning section 109 which is an alkaline
cleaner, rinse, and air blow-off. The strip is optionally
pretreated for surface energy by 110 if needed to raise the surface
energy of the metal strip. The strip is then preheated by a preheat
station 111 to raise the temperature to a laminating temperature.
The strip then enters the laminating station 112 where one or two
films are bonded to the metal strip. The strip proceeds to a post
heat oven 113 where the metal film laminate temperature is raised
to a final bonding temperature. Exit air blow offs 114 after the
post heat oven provide initial cooling. Twin contact cooling rolls
115 provide additional cooling of the metal film laminate in
preparation of winding the finished product. An optional lubricator
116 is used if a customer desires lubrication on the metal-laminate
surface. An exit looping tower 118 provides strip storage for the
winding reels 121. A pair of bridle rolls 105c,d provide tension
control on either side of the exit looping tower 118, and a
steering roll 106b provides strip tracking control. An exit shear
120 cuts the metal strip just before the winding reels 121.
[0038] The metal-polymer laminate is heated in the post treating
oven 113 to a bonding temperature. In the case of a BoPET film, a
bonding temperature has been found to be lower than the melting
point of the film by between 10 to 200.degree. F., which preserves
the film crystallinity. A preferred bonding temperature was found
to be in the range of 300-490.degree. F. for the films tested, and
also provided better chemical resistance properties.
[0039] Generally, a higher amount of crystallinity in the coating
on the final metal laminate product is needed in order to develop a
higher pencil hardness and chemical resistance. It is the normal
case to design the film crystallinity level according to a balance
between brittleness, surface hardness, and chemical resistance. For
example, a higher crystallinity without suitable elongation makes
the polymer overly brittle, which causes stamping defects. The post
heat temperature and, to a lesser extent the residence time, in the
post heat oven are important to create needed crystallinity to an
optimum value that is needed for a particular market.
[0040] In the case of using BoPET film designed to be used in the
can-making market, a BoPET film was discovered that balances
adhesion, elongation, chemical resistance, gloss, and pencil
hardness by selecting operating parameters at the bi-axially
oriented film line and also at the metal substrate--film laminating
line.
[0041] In a preferred embodiment, the bonding of the film to the
metal substrate incorporates a chemical bond. For the right preheat
and post heat temperatures a BoPET film will bond to a high and
completely commercially acceptable level. But this is not the only
embodiment possible.
[0042] In another embodiment, a tie layer is utilized to create an
enhanced bond, such as PETG (polyethylene terephthalate glycol), or
a mixture of PET and PETG.
[0043] In one particular embodiment, amorphous PETG is used as a
tie layer that offers higher improved and coating toughness in
certain situations. It was found through practical experience that
certain commercial stamping operations performed decidedly better
when a PETG tie layer was used.
[0044] For the purposes of this patent application,
i) a coating with an adhesion value of at least 43 ounces per inch
width is interpreted as a classification of 4 or 5 by ASTM test
method D3359 using a tape with an adhesion level of 43 ounces per
inch. ii) a coating that passes a pack test is based on visual
observation of adhesion and corrosion in comparison to other
products that are in commercial use. Minor cosmetic defects such as
haze or blushing are not considered a failure. iii) a coating with
a pencil hardness of a minimum of 2B means 2B or harder as measured
by ASTM test method D3363.
[0045] FIG. 2 is a generalized expression of a metal lamination
line. Each step will now be described.
[0046] Step 20: Uncoil strip--i.e. a flat rolled metal strip which
feeds a continuous operation or a batch operation. The word `strip`
is not meant to define a particular gauge range. It is meant to
mean a commercial flat rolled metal substrate.
[0047] Step 21: Clean Strip--one or both metal surfaces are cleaned
by a cleaning solution, followed by rinsing and drying sections. It
is preferable to utilize a water based cleaning solution that is
either an acid, alkaline, or soap solution. It is desirable that
the cleaning solution does not deposit any residual chemicals from
the cleaning solution, such as surfactants or emulsions. If the
cleaner is well designed, the surface energy is raised by this
processing step, and there are no spots on the surface.
[0048] After cleaning, the surface to be coated is preferably freed
of debris, oils, water, dirt, and other liquids for best adhesion.
The metal surface could be conversion coated, pretreated, or coated
with an organic primer, but these kinds of treatments are not
required for desirable adhesion. However, for some applications,
these kinds of pretreatments enhance the ability of the metal to
provide corrosion protection.
[0049] In line surface cleaning equipment comprises dip tanks,
spray systems, and electrical grid cleaning systems.
[0050] Surface energy levels out of the exit of the cleaning unit
were measured at values above 70 dynes/cm. Surface energy values at
this level are sufficient to allow the metal strip and film to bond
without additional energy surface pretreatment.
[0051] Step 22: The surface energy treating equipment is used to
raise the metal strip surface energy. The preferred equipment is
any of a treating flame, corona, or plasma. Other possible methods
include ozone treatment, ultra-high frequency electrical discharge,
UV, or laser bombardment. In one embodiment the surface energy is
raised to a minimum dyne/cm level of 45 for bonding adhesion. The
invention has found that this kind of pretreatment (along with
preheating) avoids difficulties reported by others with air
entrapment. No air entrapment of any kind was observed on a line
laminating at speeds up to 100 fpm, even when examined closely
under a microscope. In a preferred embodiment, the surface energy
level is raised above 70 dynes/cm for bonding.
[0052] Step 23: The metal strip is preheated to a temperature of
250 to 420.degree. F., depending upon the film used. Heating
methods are: flame fired oven, infrared oven, direct flame,
convection oven, induction furnace, electric resistance heating,
electric heating coils, gas fired furnace, and radiant heating.
This step can be done simultaneously with step 22 if a flame is
used.
[0053] In one embodiment, the preheater utilizes premix burner that
provides preheating of the metal to at least 200.degree. F., and
preferably to a range between 320-420.degree. F. in the case of a
BoPET film. It has been found that there has to be at least some
bond established at the laminating nip that will be maintained at
the entry of the post treating equipment. If the green strength
(initial bond) is not properly created, the film will tend to lift
off of the metal in the post treating operation and bond in a
wrinkled or bunched manner.
[0054] A temperature sensor after the preheater, which measures the
metal temperature, is preferably utilized for preheat temperature
control.
[0055] In the case of BoPET, preheating the metal substrate above
320.degree. F. provides suitable green strength from a process
standpoint. However, preheating the metal substrate too high can
cause film to stick to the laminating rolls rather than the metal
substrate. It was found that temperatures of 320 to 420.degree. F.
worked satisfactorily, depending upon the type of BoPET film
used.
[0056] In the case of BoPET, the polyester films tend to have
melting points ranging from 480 to 510.degree. F., depending upon
the type of film, as well as additives and mixtures added into the
polyester. One significant embodiment of the invention is to
maintain the preheating of the metal strip below the melting point
of the film layer in contact with the metal.
[0057] Step 24: Laminate at least one side of the metal strip by
use of a roll pair. Either or both rolls are optionally heated, but
this is not a requirement. Heating the nip roll avoids startup
issues due to a cold roll. The width and position of the film must
match the metal strip to a commercial tolerance. A second roll pair
is optionally utilized, if desired, for laminating a second film in
sequence to the first pair. If both sides of the strip are to be
laminated, any needed surface pretreatment is performed on the
second side to ensure the surface energy of the second side is
elevated prior to laminating, as well as any needed heating to
obtain the proper preheat temperature at the second roll pair.
[0058] The nip rollers press the one or both films onto the metal
substrate by use of compressed air cylinders, hydraulic cylinders,
screws, mechanical springs, or other mechanical means to create a
force. The nip rolls are optionally heated, but not so high a
temperature as to cause the films to melt or to have a preferential
adherence to the laminating nip rolls rather than to the metal
substrate. Generally, a threshold nip pressure is required to
establish an initial bonding between the film and metal substrate
without air entrapment.
[0059] Step 25a,b: Film--at least one is predominately BoPET, that
is, at least 50% polyester by weight. Tie layers, colors, and
various additives necessary for color dispersion may be added to
the polyester. Also, admixed compounds that increase pencil
hardness, provide surface lubrication, provide better processing,
provide UV resistance, or create desired gloss are optionally
added.
[0060] Step 26: The metal polymer-laminate is post heated,
preferably by a heating source, to a temperature lower than the
melting point of the BoPET film. Possible post heating ovens are
(but not restricted to): induction, flame fired, infrared, direct
flame impingement, nearly direct flame impingement, convection,
electric resistance heating, electric heating coils, and radiant
heating. An infrared sensor is preferably installed to monitor the
exit temperature to ensure proper control. Other oven temperature
sensors are optionally used to provide improved control.
[0061] For the post treating operation, it is important that the
polymer is carefully trimmed to be inside the edges of the metal
strip or within a close tolerance of the edges. The heating on the
overhanging polymer is likely to cause melting or burning of the
overhanging polymer. This can cause operational problems such as
smoking, polymer dripping, and minor flames which may cause unsafe
or unclean operational practices.
[0062] The post treating step ensures that the process provides a
reliable commercial bonding between the polyester film and the
metal substrate. The post treating step also establishes the final
commercial adhering bond.
[0063] Step 27: After the post treating step, a surface finishing
step is optionally applied to one or both surfaces of the polymer
if needed for the markets the metal-polymer laminate is being sold
to. A pinch roll is preferably used to apply a surface finish while
the polymer is still in the softened state.
[0064] Step 28: After the post treating step, a cool down rate is
performed that allows the polyester film to maintain desired
crystallinity. The cooling is performed by forced air, a liquid
spray system, one or more contact cooling rolls, or a
combination.
[0065] A temperature sensor can be used to regulate the amount of
air cooling utilized.
[0066] When laminating a BoPET film, the function of the exit
cooling section is to lower the strip temperature, preferably in a
rapid manner. One important benefit of rapid cooling is improved
gloss and clarity in the final product.
[0067] Step 29: After the cool down step, the metal-polymer
laminate is recoiled at a temperature that will not cause problems
with lap to lap shrinkage or slippage. Generally, temperatures less
than 150.degree. F. are preferred to ensure there are no winding or
storage problems.
[0068] Crystallinity in the BoPET film is measured by a
Differential Scanning calorimeter (DSC) as is known in the art.
[0069] It is desirable to have the ability to continuously run
multiple rolls of film in sequence without stopping if metal strip
storage is added to the laminating line. In this case, the ability
to switch over to films of different colors and widths is a
distinct production advantage. This adds capital cost and
operational complexity to the laminating line, but it also provides
an overall lower operating cost and a better operation. It is not
appealing to stop a line in the middle of a run for the sake of
starting a new film roll, as a customer will find yield losses and
off specification material objectionable in a finished coil.
[0070] FIGS. 3A-3B show various film--metal substrate layer
configurations. A metal substrate 304, such as tinplate or tin free
steel (TFS), is coated with a film utilizing three layers. The tie
layer 303 (or bonding layer) is utilized to facilitate bonding
between the film and the metal substrate. In one embodiment, the
tie layer utilizes an amorphous polymer, such as a PETG, to improve
the bonding. In this case, the tie layer is a PET that has been
created separately from the bulk layer 302 and top layer 301. It is
possible to create polyester film structures with different layers
in the film by utilizing different extruders, resin grades, and
mixtures of polyester. Preferably, the film comprises one, two, or
three layers, but this is not a strict requirement. A higher number
of layers could equally be used.
[0071] FIG. 4 shows a close up of a preferred embodiment of a
laminating station. A metal substrate has already been pretreated
and had the surface energy elevated as explained in FIG. 1. Film
from an upper film roll 401 with an attached rotary tension brake
404 unwinds film which passes through idler rolls and a tensiometer
roll 405 to a trimming station where one or both sides of the film
is trimmed by a razor slitter 406. The tension brake 404 is
controlled by the tensiometer roll 405 tension measurement. The
film is trimmed to match the metal substrate width to a desired
tolerance. The film roll, slitting station, idler rolls, and
tensiometer roll are mounted on a shifting frame 402 with guide
rails 403. The shifting frame 402 is used to position the film via
a film position sensor 407 in order to match the film position to
the metal substrate steel position as measured by a metal position
sensor 408 just prior to the nip rolls 409. A trim removal vacuum
tube 410 removes film trim from the slitting station. A matching
system is utilized for the lower film roll.
[0072] The overall goal is to present the film(s) at the nip roll
without wrinkle, at the correct width, and at the correct position.
This allows ordering film widths in lot sizes that are not the same
width as the metal substrate, which can provide better polymer
inventory control. The film cutting knives are preferably score
cut, razor cut, or shear slitting.
[0073] The examples following were run without any visible air
entrapment between the metal substrate and the film. Air entrapment
was not visible even when viewed under magnification capable of
seeing bubbles as small as 0.5 micron in diameter.
TABLE-US-00002 TABLE 1 Table 1 - Examples of Pack Tests at 30 Days:
Overall Product Variable Can End Observation Condition Whipped
Cream No Corrosion/ Good Delamination Cooking Pan Spray No
Corrosion/ '' Delamination Magic Sizing No Corrosion/ ''
Delamination Starch No Corrosion/ '' Delamination Hair Mousse No
Corrosion/ '' Delamination Hairspray No Corrosion/ '' Delamination
Tub & Tile Cleaner No Corrosion/ '' Delamination Brake Cleaner
No Corrosion/Delam '' (Film Slightly Cloudy) Duster No
Corrosion/Delam '' (Film Slightly Cloudy) Scrubbing Product No
Corrosion/Delam '' (Film Slightly Cloudy) SeaFoam No
Corrosion/Delam '' (Film Slightly Cloudy) Acetone No
Corrosion/Delam '' (Film Cloudy)
[0074] Laminate Example 1: A film and tin free steel laminate where
the film comprises a 15 micron biaxially oriented 2-layer PET
structure. The steel substrate was a tin free steel (TFS) at a
thickness of 0.0113''. The outer most layer of the film was
essentially PET. The inner layer of the film was 100% PETI
approximately 3 micron in thickness, and was in direct contact with
the electrolytic chromium coated steel (TFS). Adhesion of the film
to the steel was acquired through the thermal lamination process as
described within and required no additional adhesive layer.
Specifically, the steel was uncoiled and passed through a wash
process according to the teachings of this invention, by a mildly
alkaline aqueous solution, then rinsed and dried using blowoffs.
Following the cleaning process the steel was flame treated to
remove any residual moisture, the surface energy was increased and
the temperature raised to 315.degree. F. The film was brought into
contact with the steel by means of a pair of nipped rolls forming
an initial lamination bond of the film to the steel. Subsequently
the film/steel laminate was passed through an IR oven increasing
the laminate to a temperature of 350.degree. F. The film/steel
laminate was passed over a pair of 90.degree. F. cooling rolls to
reduce the laminate to a rewinding temperature and control
crystallinity of the film. The film/steel laminate exhibited good
formability during drawing processes and the film maintained
excellent adhesion to the steel throughout drawing and retort
processes.
[0075] Laminate Example 2: A film and tin free steel laminate where
the film comprises a 15 micron biaxially oriented 2-layer PET
structure. The steel substrate was a tin free steel (TFS) at a
thickness of 0.0113''. The outer most layer of the film was
essentially PET. The inner layer of the film was 99.9% PET and
approximately 3 micron in thickness and was in direct contact with
the electrolytic chromium coated steel (TFS). Adhesion of the film
to the steel was acquired through the thermal lamination process as
described within and required no additional adhesive layer.
Specifically, the steel was uncoiled and passed through a cleaning
process using a mildly basic aqueous solution, then rinsed and
dried. Following the cleaning process the steel was flame treated
to remove any residual moisture, the surface energy was increased
and the temperature raised to 380.degree. F. The film was brought
into contact with the steel by means of a pair of nipped rolls
forming an initial lamination bond of the film to the steel.
Subsequently the film/steel laminate was passed through an IR oven
increasing the laminate to a temperature of 410.degree. F. The
film/steel laminate was passed over a pair of 130.degree. F.
cooling rolls to reduce the laminate to a rewinding temperature and
control crystallinity of the film. The film/steel laminate
exhibited good formability during drawing processes and the film
maintained excellent adhesion to the steel throughout drawing and
retort processes. The resulting laminate had good resistance to
high Ph chemicals.
[0076] Laminate Example 3: A film and tin free steel laminate where
the film comprises a 15 micron biaxially oriented 2-layer PET
structure. The steel substrate was a tin free steel (TFS) at a
thickness of 0.0113''. The outer most layer of the film was 99.9%
PET and approximately 1 micron in thickness. The inner layer of the
film was essentially PET, containing <1% PETI and was in direct
contact with the electrolytic chromium coated steel (TFS). Adhesion
of the film to the steel was acquired through the thermal
lamination process as described within and required no additional
adhesive layer. Specifically, the steel was uncoiled and passed
through a cleaning process using a mildly basic aqueous solution,
then rinsed and dried. Following the cleaning process the steel was
flame treated to remove any residual moisture, the surface energy
was increased and the temperature raised to 380.degree. F. The film
was brought into contact with the steel by means of a pair of
nipped rolls forming an initial lamination bond of the film to the
steel. Subsequently the film/steel laminate was passed through an
IR oven increasing the laminate to a temperature of 400.degree. F.
The film/steel laminate was passed over a pair of 130.degree. F.
cooling rolls to reduce the laminate to a rewinding temperature and
control crystallinity of the film. The film/steel laminate
exhibited good formability during drawing processes and maintained
excellent adhesion through retort processes.
[0077] Laminate Example 4: A film and tin free steel laminate where
the film comprises a 15 micron biaxially oriented 2-layer PET
structure. The steel substrate was a tin free steel (TFS) at a
thickness of 0.0113''. The outer most layer of the film was 99.9%
PET and approximately 1 micron in thickness. The inner layer of the
film was essentially PET, containing <1% PETI and was in direct
contact with the electrolytic chromium coated steel (TFS). Adhesion
of the film to the steel was acquired through the thermal
lamination process as described within and required no additional
adhesive layer. Specifically, the steel was uncoiled and passed
through a cleaning process using a mildly basic aqueous solution,
then rinsed and dried. Following the cleaning process the steel was
flame treated to remove any residual moisture, the surface energy
was increased and the temperature raised to 380.degree. F. The film
was brought into contact with the steel by means of a pair of
nipped rolls forming an initial lamination bond of the film to the
steel. Subsequently the film/steel laminate was passed through an
IR oven increasing the laminate to a temperature of 450.degree. F.
The film/steel laminate was passed over a pair of 130.degree. F.
cooling rolls to reduce the laminate to a rewinding temperature and
control crystallinity of the film. The film/steel laminate
exhibited good formability during drawing and retort processes.
[0078] Laminate Example 5: A film and tin free steel laminate where
the film comprises a 15 micron biaxially oriented 2-layer PET
structure. The steel substrate was a tin free steel (TFS) at a
thickness of 0.0113''. The outer most layer of the film was
approximately 99.9% PET and was approximately 1 micron in
thickness. The inner layer of the film was essentially PET, and was
in direct contact with the electrolytic chromium coated steel
(TFS). Adhesion of the film to the steel was acquired through the
thermal lamination process as described within and required no
additional adhesive layer. Specifically, the steel was uncoiled and
passed through a cleaning process using a mildly basic aqueous
solution, then rinsed and dried. Following the cleaning process the
steel was flame treated to remove any residual moisture, the
surface energy was increased and the temperature raised to
410.degree. F. The film was brought into contact with the steel by
means of a pair of nipped rolls forming an initial lamination bond
of the film to the steel. Subsequently the film/steel laminate was
passed through an IR oven maintaining the laminate at a temperature
of 400.degree. F. for <10 seconds. The film/steel laminate was
passed over a pair of 130.degree. F. cooling rolls to reduce the
laminate to a rewinding temperature and control crystallinity of
the film. The film/steel laminate exhibited good formability during
drawing and retort processes.
[0079] Laminate Example 6: A film and tin free steel laminate where
the film comprises a 15 micron biaxially oriented 2-layer PET
structure. The steel substrate was a tin free steel (TFS) at a
thickness of 0.0113''. The outer most layer of the film was
approximately 99.9% PET and was approximately 1 micron in
thickness. The inner layer of the film was essentially PET, and was
in direct contact with the electrolytic chromium coated steel
(TFS). Adhesion of the film to the steel was acquired through the
thermal lamination process as described within and required no
additional adhesive layer. Specifically, the steel was uncoiled and
passed through a cleaning process using a mildly basic aqueous
solution, then rinsed and dried. Following the cleaning process the
steel was flame treated to remove any residual moisture, the
surface energy was increased and the temperature raised to
410.degree. F. The film was brought into contact with the steel by
means of a pair of nipped rolls forming an initial lamination bond
of the film to the steel. Subsequently the film/steel laminate was
passed through an IR oven maintaining the laminate at a temperature
of 500.degree. F. for <10 seconds. The film/steel laminate was
passed over a pair of 130.degree. F. cooling rolls to reduce the
laminate to a rewinding temperature and control crystallinity of
the film. The film/steel laminate exhibited excellent resistance to
high pH chemicals (up to 12.3) and good formability during drawing
processes. The film maintained excellent adhesion to the steel
throughout drawing and retort processes.
[0080] Laminate Example 7: A film and tin free steel laminate where
the film comprises a 15 micron biaxially oriented 2-layer PET
structure. The steel substrate was a tin free steel (TFS) at a
thickness of 0.0113''. The outer most layer of the film was
approximately 94.9% PET and was approximately 1 micron in
thickness. The inner layer of the film was essentially PET, and was
in direct contact with the electrolytic chromium coated steel
(TFS). Adhesion of the film to the steel was acquired through the
thermal lamination process as described within and required no
additional adhesive layer. Specifically, the steel was uncoiled and
passed through a cleaning process using a mildly basic aqueous
solution, then rinsed and dried. Following the cleaning process the
steel was flame treated to remove any residual moisture, the
surface energy was increased and the temperature raised to
410.degree. F. The film was brought into contact with the steel by
means of a pair of nipped rolls forming an initial lamination bond
of the film to the steel. Subsequently the film/steel laminate was
passed through an IR oven maintaining the laminate at a temperature
of 400.degree. F. for <10 seconds. The film/steel laminate was
passed over a pair of 130.degree. F. cooling rolls to reduce the
laminate to a rewinding temperature and control crystallinity of
the film. The film/steel laminate exhibited good formability during
drawing and retort processes.
[0081] Laminate Example 8: A film and tin free steel laminate where
the film comprises a 15 micron biaxially oriented 2-layer PET
structure. The steel substrate was a tin free steel (TFS) at a
thickness of 0.0113''. The outer most layer of the film was
approximately 94.9% PET and approximately 1 micron in thickness.
The inner layer of the film was essentially PET, and was in direct
contact with the electrolytic chromium coated steel (TFS). Adhesion
of the film to the steel was acquired through the thermal
lamination process as described within and required no additional
adhesive layer. Specifically, the steel was uncoiled and passed
through a cleaning process using a mildly basic aqueous solution,
then rinsed and dried. Following the cleaning process the steel was
flame treated to remove any residual moisture, the surface energy
was increased and the temperature raised to 410.degree. F. The film
was brought into contact with the steel by means of a pair of
nipped rolls forming an initial lamination bond of the film to the
steel. Subsequently the film/steel laminate was passed through an
IR oven maintaining the laminate at a temperature of 500.degree. F.
for <10 seconds. The film/steel laminate was passed over a pair
of 130.degree. F. cooling rolls to reduce the laminate to a
rewinding temperature and control crystallinity of the film. The
film/steel laminate exhibited good resistance to high pH chemicals
(up to 12.3) and good formability during drawing processes.
However, the laminate had poor resistance to blushing during retort
processing. The film maintained excellent adhesion to the steel
throughout drawing and retort processes.
[0082] Laminate Example 9: A film and tin free steel laminate where
the film comprises a 15 micron biaxially oriented 2-layer PET
structure. The steel substrate was a tin free steel (TFS) at a
thickness of 0.0113''. The outer most layer of the film was
approximately 89.9% PET, 10% PBT, and was approximately 1 micron in
thickness. The inner layer of the film was essentially PET, and was
in direct contact with the electrolytic chromium coated steel
(TFS). Adhesion of the film to the steel was acquired through the
thermal lamination process as described within and required no
additional adhesive layer. Specifically, the steel was uncoiled and
passed through a cleaning process using a mildly basic aqueous
solution, then rinsed and dried. Following the cleaning process the
steel was flame treated to remove any residual moisture, the
surface energy was increased and the temperature raised to
410.degree. F. The film was brought into contact with the steel by
means of a pair of nipped rolls forming an initial lamination bond
of the film to the steel. Subsequently the film/steel laminate was
passed through an IR oven maintaining the laminate at a temperature
of 400.degree. F. for <10 seconds. The film/steel laminate was
passed over a pair of 130.degree. F. cooling rolls to reduce the
laminate to a rewinding temperature and control crystallinity of
the film. The film/steel laminate exhibited good formability during
drawing and retort processes.
[0083] Laminate Example 10: A film and tin free steel laminate
where the film comprises a 15 micron biaxially oriented 2-layer PET
structure. The steel substrate was a tin free steel (TFS) at a
thickness of 0.0113''. The outer most layer of the film was
approximately 89.9% PET, 10% PBT, and was approximately 1 micron in
thickness. The inner layer of the film was essentially PET, and was
in direct contact with the electrolytic chromium coated steel
(TFS). Adhesion of the film to the steel was acquired through the
thermal lamination process as described within and required no
additional adhesive layer. Specifically, the steel was uncoiled and
passed through a cleaning process using a mildly basic aqueous
solution, then rinsed and dried. Following the cleaning process the
steel was flame treated to remove any residual moisture, the
surface energy was increased and the temperature raised to
410.degree. F. The film was brought into contact with the steel by
means of a pair of nipped rolls forming an initial lamination bond
of the film to the steel. Subsequently the film/steel laminate was
passed through an IR oven maintaining the laminate at a temperature
of 500.degree. F. for <10 seconds. The film/steel laminate was
passed over a pair of 130.degree. F. cooling rolls to reduce the
laminate to a rewinding temperature and control crystallinity of
the film. The film/steel laminate exhibited good resistance to high
pH chemicals (up to 12.3) and good formability during drawing and
retort processes.
[0084] Laminate Example 11: A film and tin free steel laminate
where the film comprises a 12 micron biaxially oriented 3-layer PET
structure. The steel substrate was a tin free steel (TFS) at a
thickness of 0.0113''. The outer most layer of the film was
essentially PET approximately 1 micron in thickness. The middle
layer of the film was PET blended with 8-10% TiO2 as a whitening
agent. The inner layer of the film contains a blend of PETG and
PET, was approximately 1 micron in thickness, and was in direct
contact with the electrolytic chromium coated steel (TFS). Adhesion
of the film to the steel was acquired through the thermal
lamination process as described within and required no additional
adhesive layer. Specifically, the steel was uncoiled and passed
through a cleaning process using a mildly basic aqueous solution,
then rinsed and dried. Following the cleaning process the steel was
flame treated to remove any residual moisture, the surface energy
was increased and the temperature raised to 375.degree. F. The film
was brought into contact with the steel by means of a pair of
nipped rolls forming an initial lamination bond of the film to the
steel. Subsequently the film/steel laminate was passed through an
IR oven increasing the laminate to a temperature of 400.degree. F.
The film/steel laminate was passed over a pair of 130.degree. F.
cooling rolls to reduce the laminate to a rewinding temperature and
control crystallinity of the film. The film/steel laminate
exhibited good formability during drawing retort processes. The
middle layer of the film being only 10 micron in thickness cannot
carry enough TiO2 to yield a laminate with the desired L* of
>80.
[0085] Laminate Example 12: A film and tin free steel laminate
where the film comprises a 23 micron biaxially oriented 3-layer PET
structure. The steel substrate was a tin free steel (TFS) at a
thickness of 0.0113''. The outer most layer of the film was
essentially PET approximately 1 micron in thickness. The middle
layer of the film was PET containing TiO2 as a whitening agent. The
inner layer of the film contains a blend of PETG and PET, was
approximately 1 micron in thickness, and was in direct contact with
the electrolytic chromium coated steel (TFS). Adhesion of the film
to the steel was acquired through the thermal lamination process as
described within and required no additional adhesive layer.
Specifically, the steel was uncoiled and passed through a cleaning
process using a mildly basic aqueous solution, then rinsed and
dried. Following the cleaning process the steel was flame treated
to remove any residual moisture, the surface energy was increased
and the temperature raised to 375.degree. F. The film was brought
into contact with the steel by means of a pair of nipped rolls
forming an initial lamination bond of the film to the steel.
Subsequently the film/steel laminate was passed through an IR oven
increasing the laminate to a temperature of 400.degree. F. The
film/steel laminate was passed over a pair of 130.degree. F.
cooling rolls to reduce the laminate to a rewinding temperature and
control crystallinity of the film. The film/steel laminate
exhibited good formability during drawing processes and retort
processes.
[0086] Laminate Example 13: A film and tin free steel laminate
where the film comprises a 23 micron biaxially oriented 3-layer PET
structure. The steel substrate was a tin free steel (TFS) at a
thickness of 0.0113''. The outer most layer of the film was
essentially PET approximately 1 micron in thickness. The middle
layer of the film was PET containing TiO2 as a whitening agent. The
inner layer of the film contains a blend of PETG and PET, was
approximately 1 micron in thickness, and was in direct contact with
the electrolytic chromium coated steel (TFS). Adhesion of the film
to the steel was acquired through the thermal lamination process as
described within and required no additional adhesive layer.
Specifically, the steel was uncoiled and passed through a cleaning
process using a mildly basic aqueous solution, then rinsed and
dried. Following the cleaning process the steel was flame treated
to remove any residual moisture, the surface energy was increased
and the temperature raised to 375.degree. F. The film was brought
into contact with the steel by means of a pair of nipped rolls
forming an initial lamination bond of the film to the steel.
Subsequently the film/steel laminate was passed through an IR oven
increasing the laminate to a temperature of 500.degree. F. The
film/steel laminate was passed over a pair of 130.degree. F.
cooling rolls to reduce the laminate to a rewinding temperature and
control crystallinity of the film. The film/steel laminate
exhibited good formability and adhesion during drawing and retort
processes.
[0087] Laminate Example 14: A film and tin free steel laminate
where the film comprises a 23 micron biaxially oriented 3-layer PET
structure. The steel substrate was a tin free steel (TFS) at a
thickness of 0.0113''. The outer most layer of the film was
essentially PET approximately 1 micron in thickness. The middle
layer of the film was PET containing TiO2 as a whitening agent. The
inner layer of the film contains a blend of PETG and PET, was
approximately 1 micron in thickness, and was in direct contact with
the electrolytic chromium coated steel (TFS). Adhesion of the film
to the steel was acquired through the thermal lamination process as
described within and required no additional adhesive layer.
Specifically, the steel was uncoiled and passed through a cleaning
process using a mildly basic aqueous solution, then rinsed and
dried. Following the cleaning process the steel was flame treated
to remove any residual moisture, the surface energy was increased
and the temperature raised to 375.degree. F. The film was brought
into contact with the steel by means of a pair of nipped rolls
forming an initial lamination bond of the film to the steel.
Subsequently the film/steel laminate was passed through an IR oven
increasing the laminate to a temperature of 400.degree. F. The
film/steel laminate was passed over a pair of 130.degree. F.
cooling rolls to reduce the laminate to a rewinding temperature and
control crystallinity of the film. The film/steel laminate
exhibited good formability and adhesion during drawing and retort
processes.
[0088] Laminate Example 15: A film and tin free steel laminate
where the film comprises a 15 micron biaxially oriented 2-layer PET
structure. The steel substrate was a tin free steel (TFS) at a
thickness of 0.0113''. The outer most layer of the film was
essentially PET. The inner layer of the film was 100% PETI
approximately 3 micron in thickness, and was in direct contact with
the electro tin plated steel (ETP). Adhesion of the film to the
steel was acquired through the thermal lamination process as
described within and required no additional adhesive layer.
Specifically, the steel was uncoiled and passed through a cleaning
process using a mildly basic aqueous solution, then rinsed and
dried. Following the cleaning process the steel was flame treated
to remove any residual moisture, the surface energy was increased
and the temperature raised to 315.degree. F. The film was brought
into contact with the steel by means of a pair of nipped rolls
forming an initial lamination bond of the film to the steel.
Subsequently the film/steel laminate was passed through an IR oven
increasing the laminate to a temperature of 350.degree. F. The
film/steel laminate was passed over a pair of 90.degree. F. cooling
rolls to reduce the laminate to a rewinding temperature and control
crystallinity of the film. The film/steel laminate exhibited good
formability and adhesion during drawing retort processes however,
the adhesion was less robust than other examples where the same
film was thermally bonded to TFS.
[0089] Laminate Example 16: A film and tin free steel laminate
where the film comprises a 15 micron biaxially oriented 2-layer PET
structure. The steel substrate was a tin free steel (TFS) at a
thickness of 0.0113''. The outer most layer of the film was
essentially PET. The inner layer of the film was a blend of PET and
PETG, was approximately 1 micron in thickness, and was in direct
contact with the aluminum (Al). Adhesion of the film to the
aluminum was acquired through the thermal lamination process as
described within and required no additional adhesive layer.
Specifically, the aluminum coil was unwound and passed through a
cleaning process using a mildly basic aqueous solution, then rinsed
and dried. Following the cleaning process the aluminum was flame
treated to remove any residual moisture, increase the surface
energy, and raise the temperature of the aluminum to a laminating
temperature of 375.degree. F. The film was brought into contact
with the aluminum by means of a pair of nipped rolls forming an
initial lamination bond of the film to the aluminum. Subsequently
the film/aluminum laminate was passed through an IR oven increasing
the laminate to a temperature of 400.degree. F. The film/aluminum
laminate was passed over a pair of 120.degree. F. cooling rolls to
reduce the laminate to a rewinding temperature and control
crystallinity of the film. The film/aluminum laminate exhibits good
formability during drawing processes and the film maintained good
adhesion to the aluminum throughout drawing and retort processes
however, the adhesion was less robust than other examples where the
same film was thermally bonded to TFS.
[0090] Summary of film testing is in tables 2 and 3 following:
TABLE-US-00003 TABLE 2 Exam- Approx Film Post ple Metal Film type
bonding bonding Ad- Pre- Lam Lam- Sub- bonded to layer Tg layer
T.sub.m hesive heat Temp inate strate metal (F.) (F.) layer (F.)
(F.) 1 TFS PETI (A) <180 <480 None 315 350 2 TFS PET (B) 180
500 None 380 410 3 TFS PET/ 180 490 None 380 400 PETI (A) 4 TFS
PET/ 180 490 None 380 450 PETI (A) 5 TFS PET (A) 180 500 None 410
400 6 TFS PET (A) 180 500 None 410 500 7 TFS PET (A) 180 500 None
410 400 8 TFS PET (A) 180 500 None 410 500 9 TFS PET (A) 180 500
None 410 400 10 TFS PET (A) 180 500 None 410 500 11 TFS PET/ 180
480 None 375 400 PETG (A) 12 TFS PET/ 180 480 None 375 400 PETG (A)
13 TFS PET/ 180 480 None 375 500 PETG (A) 14 TFS PET/ 180 480 None
375 400 PETG (A) 15 ETP PETI (A) <180 <480 None 315 350 16 Al
PET/ 180 480 None 375 400 PETG (A)
TABLE-US-00004 TABLE 3 Example Ease of Impact Food Chemical
Laminate Lamination Formability Adhesion resistance resistance
resistance 1 Excellent Good Good Good Fair Poor 2 Good Good
Excellent Good Good Good 3 Good Good Excellent Good Excellent Good
4 Good Good Excellent Good Excellent Good 5 Good Good Excellent
Good Excellent Poor 6 Good Good Excellent Good Excellent Excellent
7 Good Good Excellent Good Excellent Poor 8 Good Good Excellent
Good Excellent Good 9 Good Good Excellent Good Excellent Poor 10
Good Good Excellent Good Excellent Good 11 Excellent Good Excellent
Good Good Fair 12 Excellent Good Excellent Good Good Fair 13
Excellent Good Excellent Good Good Fair 14 Excellent Good Excellent
Good Good Fair 15 Good Good Fair Fair Fair Poor 16 Good Good Fair
Fair Fair Poor
[0091] While various embodiments of the invention have been
described, the invention may be modified and adapted to various
operational methods to those skilled in the art. Therefore, this
invention is not limited to the description and figure shown
herein, and includes all such embodiments, changes, and
modifications that are encompassed by the scope of the claims.
* * * * *